The Grenade Launcher of the GMG Jackal has a zero up to 1800, which works perfect up until 1200, then all of a sudden it seems the zero has dropped to 300, so the zero's that do not hold true are 1500 and 1800.Zero's Available with GMG 100, 200, 300, 400, 600, 800, 1000, 1200, 1500, 1800.